Asymptotic analyses of linear wave equations give extremely powerful, quantitative methods of approximation in many fields of physics. They are often called short wave or eikonal approximations for acoustic and electromagnetic waves [1]}, [2]}, where they enable an approximate construction of propagating waves or eigenmodes using rays. In quantum mechanics, they often go by the names WKB, JWKB, EBK, semiclassical, or saddle point methods (\(\hbar \rightarrow 0\)  or \(N \rightarrow \infty \)  for bosonic systems) [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, where the approximation to eigenfunctions and the propagation of wave functions are built from classical trajectories.
